[MITgcm-support] interpolate sea ice fields

[Martin Losch]

Hi David, 

so I misunderstood. I think you can area-average all fields as they are, because they all contain the fractional area (SIarea) except for maybe TICE(S) and the velocities.
I would multiply TICE(S) prior to averaging:
siTICES_new = sum(siTICES_old*siAREA_old*RAC)/sum(RAC*siAREA_old)
with siUICE/VICE it's a little more complicated because of the C-grid, but here you might just be fine with simple area averaing (but not with RAC, but with RAW and RAS).

Martin

On Aug 18, 2011, at 4:51 PM, Daiwei (David) Wang wrote:

> Hi Martin,
> 
> Thanks for the comment.
> 
> Computationally sub-sampling should be OK. But I hope the interpolated fields best approximate the original fields. For example, since one new grid cell comprises 25 old grid cells, for siAREA,
> 
> siAREA_new = sum(siAREA_old*RAC)/sum(RAC)
> 
> would conserve total sea ice concentration (where RAC is the cell area of the old grid), and presumably be a better choice than sub-sampling. But I'm not sure about other sea ice fields.
> 
> Thanks,
> David
> 
> On 8/18/11 4:10 AM, Martin Losch wrote:
>> Hi David,
>> 
>> the model should be able to deal with subsampled sea-ice fields (i.e. not blow up), if that's the question.
>> 
>> Martin
>> 
>> On Aug 17, 2011, at 8:01 PM, Daiwei (David) Wang wrote:
>> 
>>> Hi,
>>> 
>>> I intend to interpolate a set of pickup files to a grid five times (horizontally) coarser than the original grid, and wonder what the most appropriate means of interpolation is for sea ice fields, which are
>>> 
>>> $ cat pickup_seaice.0000000001.meta
>>> nDims = [   2 ];
>>> dimList = [
>>>  3060,    1, 3060,
>>>   510,    1,  510
>>> ];
>>> dataprec = [ 'float64' ];
>>> nrecords = [    13 ];
>>> timeStepNumber = [      26280 ];
>>> /* modelTime = [  3.153600000000E+07 ];*/
>>> nFlds = [    7 ];
>>> fldList = {
>>> 'siTICES ' 'siAREA  ' 'siHEFF  ' 'siHSNOW ' 'siHSALT ' 'siUICE  ' 'siVICE'
>>> };
>>> 
>>> Will naive sub-sampling of every five grid points do, or area-weighted averaging?
>>> 
>>> Thanks,
>>> David
>>> 
>>> 
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>>> MITgcm-support mailing list
>>> MITgcm-support at mitgcm.org
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>> 
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> 
> -- 
> Daiwei Wang, Postdoctoral Associate
> 54-1517, Program in Atmospheres, Oceans, and Climate
> Department of Earth, Atmospheric and Planetary Sciences
> Massachusetts Institute of Technology
> 
> 
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